jhjenkins4th wrote:I did some testing on the POI shift due to a suppressor mounted on my PS90 SBR 10.3”. On a previous trip to a public range, I zeroed my PS90 without a suppressor out to 50yds. When I attached my Specwar762 (with trifecta mount) to my PS90, it wouldn’t even hit paper.

This past weekend I went to my private range test some new reloads. So I set up my chronograph at 10ft and cardboard directly behind it, to confirm my rounds were not keyholing before mounting my suppressor. The PS90 was strapped tightly into a bench rest to prevent shooter error. Without suppressor, the shots hit tighly without keyhole. I then attached suppressor to the trifecta mount. I shot 2 rounds and the new bullet holes were hitting roughly 2 inches lower on the cardboard….at just 10ft!!!! Thankfully it did not hit the chronograph. Velocity was similar suppressed/unsuppressed.

This POI shift explains why I was not hitting paper on my previous range trip. This same suppressor on my 300blk AR15 has very little POI shift. I assume the size/weight of this suppressor combined with the skinny PS90 barrel may be causing the barrel to droop downward maybe… When I had shot my PS90 with a 22Sparrow a long time ago, I did not observe such a POI shift but did not really measure it either. My barrel was cut down by TROS a couple years ago and don’t think that is the issue at all.

For the remainder of my reload testing, I took the suppressor off and had great test results for my reloads. At the end of my session, I had some fun finishing off 2 mags of SS197 ammo I had laying around. I reattached the suppressor so I could see how the shots hit with the POI shift. The two mags being used were ATI brand and were both having multiple jams through the rapid fire session. At one jam a round failed to feed completely and resulted in a round with the blue tip ruined…so that round was discarded. After the session was over, I noticed that the Specwar had an end cap strike. I know there are not concentricity issues so it amazed me that this happened. The only thing I can think of is maybe another round got damaged during one of the jams caused it to keyhole. Thankfully the damage only appears to be cosmetic. No baffles were touched.

I think the jams were due to the ATI mags, as upon inspection they would not even feed the next round while messing with the rotary section with my fingers. Might be a combination of mag being dirty and weak mag spring, but the mags are nearly brand new. The mag I was using during reload testing was a FN brand mag.

Long winded but I just wanted to put my experience out there. I will not be running my Specwar on this PS90 any longer due to POI shift and possibility of another end cap strike.
Any input or thoughts are welcome.

Pics of the end cap strike

I went to the range today and tried my specwar 762 on my ps90 and I didn't have the same issue you had. I didn't have any strikes and even more shocking I didn't have a noticeable POI shift. I could only shoot out to the 25 yard line because it was indoor but I didn't have any issues. Here is mine.